The response of a human system or organization to hazards may often be viewed in terms of
self-organized criticality. That is, the operating point of the system, in terms of resources,
scheduling, work methods, safety barriers, etc, evolves until a balance is reached between
competing pressures such as the simultaneous desires for high work productivity and a low
probability of accidents. From a safety viewpoint, the system may be viewed as having
migrated away from high safety to a point where it is "on the edge of chaos". Chaos in this
case may be defined as a situation where a small perturbation may or may not be absorbed
by the system; the outcome is often tragic. At this operating point "on the edge", the
frequency of small incidents already gives an indication that more severe incidents are
distinctly possible, even though much less likely to occur. Empirically, a power law relates the
frequencies of different severity events.
Examples of balanced systems or systems with power laws are air traffic control, powerline
maintenance work, the Great Fire of London, and the King's Cross Underground Fire.
In the safety literature, Risk Compensation is a theory claiming that most safety improvements
will be nullified because humans will increase their exposure to or level of hazard and claim
the benefit in some other currency such as time or performance, while keeping the net risk
unchanged. Driving faster and following more closely after the introduction of seat belts, anti-
lock brakes and airbags are often cited as examples. This is often described as being governed
by a "risk thermostat" whereby a target level of acceptable risk is maintained. The insight
provided by self-organization is that the feedback provided by small incidents, and the
protection against severe events afforded by a power law, allows the operating point to be set
"on the edge."
Ultimately, it is hoped that theories of self-organized systems will lead to better management
indicators of safety risk and lead to insights when organizational or economic changes may
be inadvertently moving a system into an unacceptable regime.